stopping frequently to charge the battery (which can take hours). The vehicle owner therefore accrues the benefits of using cheaper and less carbon-intensive electric power for most driving, while maintaining the ability to embark on longer trips with the same vehicle. When a range extender uses conventional fuels they can re-fuel at regular fuel stations, which provides them with a similar driving range to conventional automobiles. As an REEV is only propelled by the electric motor it can do away with the weight and cost associated with the gearbox transmission system typically used in internal combustion engine cars. Further, as the range extender does not need to increase or decrease output in line with the power needs of the vehicle (this task is handled by the electric motor) the range extender can be sized to satisfy the vehicle's average power requirement rather than its peak power requirement (such as when accelerating). The range extender can also operate much closer to its most efficient rotational speed. These design features allow an REEV to convert fossil fuel energy to electric power and vehicle motion relatively efficiently. Generations The first generation range extenders are off the shelf internal combustion engines. The second generation consists of piston engines with new designs from scratch for fairly constant load in series hybrids. They include the wankel engines, rotary combustion engines and free piston engines. The third generation are micro turbines and fuel cells that work at constant load. CARB regulation According to 2012 Amendments to the Zero Emission Vehicle Regulations adopted in March 2012 by the California Air Resources Board (CARB), a range-extended battery-electric vehicle, designated as BEVx, should comply, among others, with the following criteria: The vehicle must have a rated all-electric range of at least . This is higher than the required of a zero-emission vehicle; The auxiliary power unit (APU) must provide range less than or equal to battery range; The APU must not be capable of switching on until the battery charge has been depleted; The vehicle must meet super ultra low emission vehicle (SULEV) requirements; and The APU and all associated fuel systems must comply with zero evaporative emissions requirements. Applications Range extenders are commonly used in marine (autonomous underwater vehicle), aircraft and Generator/Utility, automotive and hybrid electric vehicle applications. Automotive Chevrolet Volt General Motors describes the Chevrolet Volt as an electric vehicle equipped with a 16 kWh battery plus a